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Access Microbiology open research platform logo - Volume 4, Issue 9, 2022

Volume 4, Issue 9

Volume 4, Issue 9, 2022

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  • Research Articles

      • Sorbitol non-fermenting and . O157: prevalence and antimicrobial resistance profile of strains in slaughtered food animals in Southeast Nigeria

        https://doi.org/10.1099/acmi.0.000433

        Antimicrobial resistance (AMR) is one of the greatest global health challenges. Reliable monitoring of AMR in bacteria in food animals is critical in order to devise mitigation strategies and empiric treatment of infections associated with the organisms. The aim of this study was to isolate sorbitol non-fermenting (SN-F) from food animals (broiler chickens, cattle and pigs) slaughtered at Ikpa Market, Nsukka, Enugu State, Southeast Nigeria, detect O157 and determine the antimicrobial resistance profile of the strains. A total of 388 faecal samples were collected from randomly selected broiler chickens (=155), cattle (=129) and pigs (=104). Isolation of SN-F was done using tryptic soy broth and cefixime- and potassium tellurite-supplemented sorbitol MacConkey agar (CT-SMAC). SN-F strains were confirmed biochemically and O157 detected serologically using specific O157 latex agglutination test kit. The antimicrobial resistance profile of all strains was established using the disc diffusion method. Overall, 52 (13.4 %) SN-F strains were recovered from the broiler chickens (=31), cattle (=12) and pigs (=9). A significant association (χ=9.70; <0.05) was observed between the prevalence of SN-F and animal species. O157 was detected in two of the samples, representing 0.51% of the 388 samples processed. All the strains were resistant to at least one antimicrobial agent tested and 76% were multidrug resistant (MDR). The mean multiple antibiotic resistance indices (MARI) for isolates from chickens, cattle and pig were 0.32, 0.18 and 0.23, respectively. This study showed that a considerable percentage of food animals slaughtered in Nsukka Southeastern Nigeria are potential reservoirs of multiple-drug-resistant SN-F including O157 that could spread to humans and the environment.

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    • The stressosome is required to transduce low pH signals leading to increased transcription of the amino acid-based acid tolerance mechanisms in

      https://doi.org/10.1099/acmi.0.000455

      Increasing proton concentration in the environment represents a potentially lethal stress for single-celled microorganisms. To survive in an acidifying environment, the foodborne pathogen quickly activates the alternative sigma factor B (σ), resulting in upregulation of the general stress response (GSR) regulon. Activation of σ is regulated by the stressosome, a multi-protein sensory complex involved in stress detection and signal transduction. In this study, we used strains harbouring two stressosome mutants to investigate the role of this complex in triggering expression of known amino acid-based resistance mechanisms in response to low pH. We found that expression of glutamate decarboxylase () and arginine and agmatine deiminases ( and , respectively) were upregulated upon acid shock (pH 5 for 15 min) in a stressosome-dependent manner. In contrast, transcription of the operons ( and ), which encode enzymes for the -arginine biosynthesis pathway, were upregulated upon acid shock in a stressosome-independent manner. Finally, we found that transcription of , which encodes a transcriptional regulator of the and operons, was largely unaffected by acidic shock. Thus, our findings suggest that the stressosome plays a role in activating amino acid-based pH homeostatic mechanisms in . Additionally, we show that genes encoding the -arginine biosynthesis pathway are highly upregulated under acidic conditions, suggesting that intracellular arginine can help withstand environmental acidification in this pathogen.

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